This invention relates to concrete pumps, and, more particularly, to a concrete pump with a hopper and a pivotable S-tube valve assembly.
Concrete pumps are well known in the construction industry and are used for pumping concrete or other pumpable construction materials. Concrete pumps are described, for example, in U.S. Pat. Nos. 3,612,730, 3,897,180, 4,241,641, and 6,305,916.
Most concrete pumps which are currently being manufactured include two concrete pumping cylinders and an S-shaped tube valve for alternately connecting the outlet end of each pumping cylinder to the discharge conduit of the concrete pump. The S-tube valve is pivotably mounted in a concrete hopper. As the piston in one of the pumping cylinders moves toward the hopper to pump concrete through the S-tube valve to the discharge conduit, the piston in the other pumping cylinder retracts away from the hopper to draw concrete into the cylinder.
A typical S-tube valve assembly is described in U.S. Pat. No. 6,305,916. The valve assembly includes an S-tube and a mounting plate for the S-tube which is pivotally mounted on the hopper. A wear ring is mounted in an opening in the valve assembly and engages a wear plate on the hopper.
U.S. Pat. No. 6,305,916 also describes an S-valve and hopper assembly which is pivotally mounted on the frame or chassis of the concrete pump. The valve and hopper assembly can swing away from the outlet ends of the pumping cylinders. The inlet end of the S-tube valve is thereby exposed for easy cleaning. The outlet ends of the pumping cylinders are also exposed to permit the piston seals to be changed.
However, the wear plate and wear ring which provide a seal as the S-tube valve pivots within the hopper are mounted inside the hopper. The wear plate and wear ring therefore cannot be easily inspected or changed. Those parts can be changed only after the S-tube valve is disassembled.